Heroku buildpack for Rust
This is a Heroku buildpack for Rust with support for cargo and rustup. Features include:
- Caching of builds between deployments.
- Automatic updates to the latest stable Rust by default.
- Optional pinning of Rust to a specific version.
- Support for
exportso that other buildpacks can access the Rust toolchain.
- Support for compiling Rust-based extensions for projects written in other languages.
Here are several example projects:
- rust-buildpack-example-actix uses the popular Actix framework, and runs on stable Rust.
- rust-buildpack-example-rocket uses the innovative Rocket framework, which currently requires nightly Rust.
Using this buildpack
To deploy an application to Heroku, we recommend installing the Heroku CLI.
If you're creating a new Heroku application,
cd to the directory containing your code, and run:
heroku create --buildpack emk/rust
This will only work if your application has a
Cargo.toml and uses
git. If you want to set a particular name for application, see
heroku create --help first.
To use this as the buildpack for an existing application, run:
heroku buildpacks:set emk/rust
You will also need to create a
Procfile pointing to the release version of your application, and commit it to
hello is the name of your binary.
To deploy your application, run:
git push heroku master
Running Diesel migrations during the release phase
This will install the diesel CLI at build time and make it available in your dyno. Migrations will run whenever a new version of your app is released. Add the following line to your
and this one to your
release: ./target/release/diesel migration run
Specifying which version of Rust to use
By default, your application will be built using the latest stable Rust. Normally, this is pretty safe: New stable Rust releases have excellent backwards compatibility.
But you may wish to use
nightly Rust or to lock your Rust version to a known-good configuration for more reproducible builds. To specify a specific version of the toolchain, use a
rust-toolchain file in the format rustup uses.
Note: if you previously specified a
VERSION variable in
RustConfig, that will continue to work, and will override a
Combining with other buildpacks
If you have a project which combines both Rust and another programming language, you can insert this buildpack before your existing one as follows:
heroku buildpacks:add --index 1 emk/rust
If you have a valid
Cargo.toml in your project, this is all you need to do. The Rust buildpack will run first, and your existing buildpack will run second.
But if you only need Rust to build a particular Ruby gem, and you have no top-level
Cargo.toml file, you'll need to let the buildpack know to skip the build stage. You can do this by adding the following line to
Customizing build flags
If you want to change the cargo build command, you can set the
RUST_CARGO_BUILD_FLAGS variable inside the
RUST_CARGO_BUILD_FLAGS="--release -p some_package --bin some_exe --bin some_bin_2"
The default value of
--release. If the variable is not set in
RustConfig, the default value will be used to build the project.
Using the edge version of the buildpack
emk/rust buildpack from the Heroku Registry contains the latest stable version of the buildpack. If you'd like to use the latest buildpack code from this Github repository, you can set your buildpack to the Github URL:
heroku buildpacks:set https://github.com/emk/heroku-buildpack-rust
If you need to tweak this buildpack, the following information may help.
Testing with Docker
To test changes to the buildpack using the included
Then make sure there are no Rust-related *.so files getting linked:
This uses the Docker image
heroku/cedar, which allows us to test in an official Cedar-like environment.
We also run this test automatically on Travis CI.